The poor prognostic significance of deletions of derivative chromosome 9 in Chinese patients with chronic myelogenous leukemia

Abstract

17535 Background: Chronic myeloid leukemia (CML) is characterized by formation of the BCR/ABL fusion gene, usually as a consequence of the Philadelphia (Ph) translocation between chromosomes 9 and 22. Deletions of the derivative 9 chromosome [der(9)] in 10- 15% of CML patients with a standard Ph translocation and in >30% of CML patients with a variant Ph translocation. Subsequent studies demonstrated that CML patients who carry a der(9) deletion progress more rapidly to blast crisis and have a shorter survival than those without a deletion. The characteristics of Chinese patients with each hematologic malignancy compared with those in other countries have not yet been clarified. This prompted us to perform molecular and cytogenetic analyses on Chinese patients with CML. Methods: To study the incidence and the prognostic significance of the derivative chromosome 9 [der(9)] deletions in on Chinese patients with CML, a series of 48 BCR/ABL positive Chinese CML blast crisis (CML-BC) patients were investigated using dual colour dual fusion BCR/ABL probe and fluorescence in situ hybridization (FISH). Results: Eight (16.7%) cases showed der(9) deletions, and the deletions were also existed in chromosome preparations made at diagnosis. The estimated median length of chronic phase for patients with der(9) deletions was 18 months (range 4–38 months) compared to 48 months (range 0–204 months) for patients without deletions. Kaplan-Meier analysis revealed a striking difference in length of chronic phase between with and without der(9) deletions, and this difference was highly significant by log-rank analysis. Der(9) deletions are not associated with increased karyotypic instability. There was no difference in the probability of the der(9) deletions between the cases transformed to acute nonlymphocytic leukemia (ANLL) and those to acute lymphoid leukemia (ALL). Conclusions: The results indicate that FISH technique could effectively detect the der(9) deletions. Der(9) deletions occur at the time of Ph translocation. CML patients with der(9) deletions have more rapid process and poorer prognosis. Deletion status is a powerful prognostic factor for patients with CML. Der(9) deletions might not lead to transformation to specific type in CML. No significant financial relationships to disclose.